Subsurface well control apparatus and method

ABSTRACT

A new and improved method and apparatus for reliably and accurately controlling one or more operations of subsurface well drilling and well control equipment, and for reducing the likelihood of inadvertent actuation of such apparatus from stray or other undesired or spurious signals, is disclosed.

United States Patent [191 Maroney et al. 1451 June 5, 1973 [54]SUBSURFACE WELL CONTROL 2,41 1,696 11/1946 Silverman et al. ..340/18 NCAPPARATUS AND METHOD 3,631,398 12 1971 Houghton ..340/168 R 3,333,2397/1967 Silverman ..340/l8 NC [761 lnvemmsi w-MamnebBox 44,Mark'3,150,321 9/1964 Summers ..340/18 NC ham; Lester Halhcote, BOX 356,3,423,733 1/1969 Aver et a1. ..340/l68 R Conroe; Thomas W. Sparkman, Boxfi gir Post Lane Houston Primary Examiner-Benjamin A. Borchelt a 0Assistant Examiner-H. A. Birmiel [22] Filed: Feb. 17, 1971Attorney-Pravel, Wilson & Matthews 21 Appl. N0; 116,153 [57] ABSTRACT 52U.s.c1. ..340/l8 P 166/65 R 340/18 NC A new and impmved and aPWtus for340/18 R 340/168 liably and accurately controlling one or more opera-511 161. c1. ..G 0lv mo tions of Subsurface drilling and [58] Field ofSearch ..340/18 NC, 18 P, equipment, and for reducing the likelihood ofinadver- 340 1 7 R, 1 3 R; 32 13 1 5 R tent actuation of such apparatusfrom stray or other undesired or spurious signals, is disclosed. [56]References Cited UNITED STATES PATENTS 11 Claims, 7 Drawing Figures3,543,042 11/1970 Hart ..340/l8 P 105 MAGNET/C 00/25 7/ 2/6 H. --;'-Z/qEEC'E/VEIE J 44/0 colt/r201. L

c/Ecu/Tey WELL. 7-001. 0/2 i\ 5 IMS 772 z/ vr I an I Patented June 5,1973 4 Sheets-Sheet 2 INVENTORJ pmef W14 & Maul-aw:

HTTOR/VE YS SUBSURFACE WELL CONTROL APPARATUS AND METHOD BACKGROUND OFTHE INVENTION 1. Field of the Invention The present invention relates tomethods and apparams for controlling operations of subsurface welldrilling and well control equipment.

2. Description of the Prior Art In the prior art apparatus and methodsfor controlling down hole or subsurface well equipment, radiatedelectromagnetic energy was sent by a transmitter at the surface andsensed by the subsurface apparatus. The prior art apparatus often sensedstray or spurious undesired radio signals which would cause operation ofthe downhole equipment at a time when operation was not desired orwanted,damaging the well and equipment and causing needless expense andwaste. Highly sensitive and accurate radio receiving circuitry toincrease the selectivity and sensitivity of the downhole apparatus wereaffected by the temperatures of the earth adjacent the well and by thejostling and vibratory forces when such circuitry was being lowered intothe well and were thus undesirable.

The use of magnetic structure, or acoustic signals or mechanicalvibrations as signals to initiate downhole control did not overcome theproblem since such signals hade to be converted into electrical signalsupon receipt by the downhole apparatus, limiting the sensitivity of theapparatus to that of the conversion equipment. Further, control of morethan one downhole operation by other than electrical signals wasdifficult to achieve.

SUMMARY OF THE INVENTION Briefly, the present invention provides a newand improved method and apparatus for controlling the operation ofsubsurface well drilling and well control equipment whereinpredetermined numbers of pulses of electrical current at a preselectedfrequency are sent through the earth in the vicinity of the subsurfacewell equipment and are sensed by an inductive coil. Pulses or signals ofother than the preselectd frequency are excluded by a selective filterand the pulses of the preselectd frequency are counted. A controlsignal, controlling operation of the subsurface well equipment, isformed in response to the presence of a predetermined count. Pluralsubsurface well tools and equipment as well as plural functions therein,each assigned a predetermined operating code number of pulses, may beselectively controlled in response to transmission and receipt of thepredetermined code number in the method and apparatus of the presentinvention.

It is an object of the present invention to provide a new and improvedsubsurface well control apparatus and method.

It is an object of the present invention to provide a new and improvedmethod and apparatus for subsurface well control which is not operatedby stray or spurious signals.

It is an object of the present invention to provide a new and improvedmethod and apparatus which selectively controls plural subsurface welltools and equipment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view ofa wellusing the method and apparatus of the present invention;

FIG. 2 is an elevation view of the downhole portion of the apparatus ofthe present invention;

FIG. 3 is a schematic electrical block diagram of the apparatus of thepresent invention;

FIG. 4 is a schematic electrical circuit diagram of the reciever/bufferof FIG. 3;

FIG. 5 is a schematic electrical circuit diagram of a portion of thetransmitter of FIG. 3;

FIG. 6 is a schematic electrical circuit diagram of the frequencyselective filter of FIG. 3; and H FIG. 7 is a schematic electricalcircuit diagram of the coded station control circuit of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, the letter Adesignates generally the apparatus of the present invention forelectrically controlling the operation of a valve, coring device,explosive device or other subsurface or downhole well drilling or wellcontrol equipment in land based wells or offshore wells. The apparatus Aincludes a transmitter section T and a subsurface control equipmentsection S (FIG. 1).

The transmitter section T is located in the vicinity of a derrick D anda platform P of a well at the surface of the earth. The transmitter Tincludes an electrical transformer 10 having primary and secondarywindings to receive an incoming pulse of current in the primary windingsand transfer such to the secondary windings while increasing themagnitude of such current. An electrical conductor 11 connects oneterminal of the secondary coil of the transformer 10 to a casing 12 ofthe well at a connection 11a. A second terminal of the secondary coil ofthe transformer 10 is electrically connected to a remote ground 14 by anelectrical conductor 13. The remote ground 14 may be a casing of anotherwell not connected to the well having the casing 12, a large sheet ofmetallic foil buried slightly beneath the surface of the earth, a railof a nearby railroad track, a ground of a nearby power transmission lineor any other suitable metallic structure which is not electricallyconnected to the casing 12 in order that pulses of electrical currentwill be conducted by the earth between the casing 12 and the ground 14when the transformer 10 is receiving current, as will be more evidenthereinbelow.

The primary of the transformer 10 has a larger number of windings thanthe secondary, in order that the transformer 10 will increase themagnitude of the current during transfer of such current from theprimary to the secondary. The primry of the transformer 10 is connectedin a series electrical circuit arrangement with a battery 15 or othersuitable source of direct current electrical power and the switch 16which opens and closes in response to electrical pulses from adriver/buffer 32 (FIG. 3) of the transmitter T. As the switch 16 closesand opens in response to the receipt of a pulse from the driver/buffer32, electrical current from the battery 15 flows through the primarycoil of the transformer 10 during the interval that the switch 16 isclosed. The current in the primary coil is increased in the transformer10 and induced into the secondary coil of the transformer 10, causing apulse of electrical current to be transmitted through the earth betweenthe casing 12 and the ground 14 adjacent the well with which theapparatus A is being used.

The subsurface equipment control portion S of the apparatus A is mountedwithin a chamber a of a tubular member 20 which may be mounted in adrill string when the apparatus is used with well drilling equipment orwhich may be lowered by a wireline when the apparatus A is used withwell control or testing equipment in a well.

The subsurface equipment control portion S includes a sensing coil 21(FIG. 2), a receiver/buffer 40 (FIG. 3), a frequency selective digitalfilter 60 (FIG. 3), a digital filter oscillator 61, a coded stationcontrol circuit 70 and a switch which operates in response to an outputsignal from the control circuit 70, as will be more evident hereinbelow.The buffer. 40, the filter 60, the oscillator 61 and the control circuit70 are mounted in a capsule or container 23 within the chamber 200. Thecontainer 23 is mounted with the tubular member 20 by a suitablestructure of the well known type.

The sensing coil 21 (FIG. 2) includes a spool shaped laminated magneticcore 21a which is mounted within the chamber 20a of the tubular member21 by being snugly fit against the inner wall 20b of the tubular member20 or by other suitable structure. A coil 21b formed by a plurality ofturns of an electrically conductive wire is mounted about the centerportion of the spool shaped core 21 and produces an electrical currentin response to changes in the magnetic flux in the core 21a. A pair ofelectrical conductors 21c and 21d connect the coil 21b to thereceiver/buffer 40 within the container 23. The core 21a senses thechanges in magnetic flux in the earth formed by the passage of pulses ofelectrical current through the earth induced by the transmitter portionT of the apparatus A, and such changes in flux cause a current to flowin the coil 21b which is conducted to the receiver/buffer, as will bemore evident hereinbelow.

A pair of output conductors 24a and 24b are electrically connected withthe control circuit 70 within the container 23 and pass from thecontainer 23 into the chamber 20a. The conductor 24a electricallyconnects the control circuit 70 to an electrically compatible switch ina subsurface tool or instrument E whose operation is to be controlled bythe apparatus A of the present invention. If plural subsurface tools orinstruments are to be controlled by the apparatus A of the presentinvention, as will be more evident hereinbelow, a plurality of outputconductors connects each of such tools or instruments individually to acontrol output generator within the control circuit 70. The electricalconductor 24b connects the control circuit 70 to an electrical referenceor common ground, for example the tubular member 20.

The switch in the tool or instrument E receiving the control signal overthe conductor 24a may be a transistor, a relay, a silicon-controlledrectifier, or other suitable electrically operated switching devicewhich responds to an input signal of electrical current and operates topermit the flow of electrical current from a self contained power sourcewithin the tool or instrument to operate such tool or instrument.

The tool or instrument E may be for example an explosive charge, asolenoid to operate a valve or other subsurface mechnical structure, orother subsurface well drilling and well control equipment, as has beenpreviously set forth. An electrical conductor 24c connects the switchwithin the tool E to an electrical common or reference in order that thecurrent from the control circuit will pass through such switch tooperate the tool E, as will be set forth hereinbelow.

The transmiter section T includes a transmitter circuit 50, atransmitter oscillator 51 and a drive/buffer 32 in addition to :thestructure previously set forth. The driver/buffer 32 is an impedancematching buffer of the well-known type which matches the output of thetransmiter circuit 50 to the impedance of the relay or other controlapparatus which operates the switch 16 in the transmitter T.

The transmitter circuit 50 receives a coded input signal in accordancewith the equipment to be controlled, or the operation to be performed bysuch equipment, and forms such input signal into a train of pulses of apredetermined frequency which are converted in the impedance matchingdriver/buffer 32 to a proper level to cause the apparatus controllingswitch 16 to close in response to each pulse. As has been set forthhereinabove, each closure of the switch 16 sends a pulse of electricalcurrent through the earth adjacent the well. Thus, the transmittercircuit 50 controls the transmitter section T to send a preselectedcoded number of pulses at a predetermined frequency through the earthadjacent the well to control the operation of subsurface well drillingor well control equipment E through the subsurface equipment controlportion S.

The transmitter 50 (FIG. 5) includes the transmitter oscillator 51, atransmitter binary counter 52, a transmit control switch 53, a controlNAND gate 54, a control NAND gate 55, a control flip-flop 56 and ablocking flip-flop 57. An input signal corresponding to the pre-selectednumber of pulses to be transmitted is loaded into the transmittercounter 52 under the control of the switch 53, the gates 54 and 55 andthe flip flop 56, as will be more evident hereinbelow. Subsequently, theswitch 53, the gatea 54 and 55 and the flipflop 56 control the flip-flop57 to permit pulses equal in number to the input count stored in thecounter 52 to pass from the oscillator 51 through the flip-flop 57 tothe driver/buffer 32 to open and close the switch 16 once for each ofthe pulses.

The switch 53 is a single pole, double throw switch having an arm 53awhich connects a contact 53b to an electrical ground when the switch 53is in a load position to cause the input count to be loaded into thetransmitter counter 52. The arm 53a connects a contact 530 of the switch53 to ground when the switch 53 is in a transmit position, controllingthe gates 54 and 55 and the flip-flop 56 to allow the blocking flip-flop57 to pass pulses from the oscillator 51 to the driver/buffer 32. Aninput 55a of the gate 55 is connected to ground, or logical 0 when theswitch S3 is in the load position. The input 55a receives a logical Ithrough a current limiting resistor 53e from a positive power supplyterminal 53b when the switch 53 is in the transmit position. An input54a of the gate 54 receives a logical 0 when the switch 53 is in thetransmit position, grounding such input through the contact 53c and thearm 53a. The input 540 receives a logical I from the positive powersupply terminal 53d through a current limiting resistor 53f when theswitch 53 is in the load position.

The second input 55b of the gate 55 is connected to an output terminal54b of the gate 54 and receives the output of the gate 54 as one input.Similarly, an output 550 of the gate 55 is connected to asecond input540 of the gate 54 to provide the output of the gate 55 as an input tothe gate 54.

When the switch 53 is in the load position, as has been set forthhereinabove, the input 550 receives a logical O and the input 540receives a logical l. The logical l at the input 54a drives the output54b of the gate 54 to a logical O, which is furnished ot the input 55bof the gate 55. Presence of a logical 0 level at the inputs 55a and 55bcauses the output 55c of the gate 55 to assume a logical I level. Thus,when the switch 53 is in the load position, the output terminal 55c ofthe gate 55 is a logical 1.

Presence of a logical l at the output 54b drives the output 550 of thegate 55 to a logical 0. Thus, the output terminal 55c is a logical 0when the switch 53 is in the transmit position.

An electrical conductor 56a connects the output 550 of the gate 55 to aJ input 56b and a clock pulse 560 of the flip-flop 56. The flip-flop 56is a master-slave flipflop, reading in data into the J input 56b inresponse to a positive going clock signal, and transferring such signalto a Q output terminal 56e in response to a negative going clock signal.A K input 56b of the flip-flop 56 is grounded. The Q output terminal 56eof the flip-flop 56 is electrically connected by a conductor 56f to aload input 52b of the transmitter counter 52 and by an electricalconductor 56g to a clear input 57e of the flip-flop 57. A clear input56h of the flip-flop 56 is electrically connected to a borrow outputterminal 522 of the counter 52 by an electrical conductor 52f.

The transmitter counter 52 receives an input binary signal over aplurality of input terminals 52a corresponding to the binary countequaling the number of pulses to be sent by the transmitter T. A clearinput 52d of the counter 52 is connected to ground to preventinadvertent clearance of the loaded input binary number before theproper count is achieved. An up count input terminal 52g of the counter52 is connected through a current limiting resistor 52h to a positivepower supply terminal 52i in order to prevent the counter 52 fromcounting upwardly. A down count input terminal 52c of the counter 52 iselectrically connected by a conductor-57f to a Q output terminal 57d ofthe blocking flip-flop 57. The transmitter counter 52 receives a binaryinput count corresponding to the number of pulses desired to betransmitted over the conductors 52a and counts downwardly from suchbinary count in reponse to pulses furnished to the down count input 52cby the flip-flop 57 over the conductor 57;. The counter 52 continues itscount downwardly until. a count of zero is reached at which time alogical O is provided to the clear input 56h of the flip-flop 56 overthe conductor 52f.

The transmitter oscillator 51 is an oscillator of the well-known typeand oscillates at a preselected frequency of twice the frequency of thesignal output of the transmitter section T. An electrical conductor 51aconnects the transmitter oscillator 51 to a J input 57a, a clock pulseinput 57b, and a K input 570 of the flipflop 57. The flip-flop 57changes state at the Q output terminal 57d in response to each positivezero crossing in the output signal from the transmitter oscillator 51,dividing the output frequency of the oscillator 51 by two and providingan electrical signal of the preselected frequency to the driver/buffer32 over an electrical conductor 57g and to the transmitter counter 52over the electrical conductor 57f.

In the operation of the transmitter 50, a push-button switch or othersuitable means is electrically connected to the input conductors 52a andused to provide electrical signals over such conductors corresponding tothe number of pulses to be transmitted. As will be more evident below,upon completion of the previous transmission, the Q output 56e is alogical O, and such signal is presented to the load input 52b of thecounter 52, allowing the input count to enter the counter 52.

If not already in the load position, the switch 53 is moved to the loadposition, providing a logical l at the output terminal 550 of the gate55. The logical l is received at the inputs 56b and 56c of the flip-flop56, and stored within the flip-flop 56. On receipt of a negative goingpulse at the clock pulse input 56c, the logical l is tranferred to the Qoutput 56e of the masterslave flipflop 56. The logical O at theflip-flop 56 remains until the negative going clock signal is conductedto the blocking flip-flop 57, preventing such flip-flop from operatingby maintaining the Q output terminal 57d at a logical 0.

When it is desired to transmit, the switch 53 is moved from the loadposition to the transmit position, allowing current to flow fromterminal 53d into the input 55a, driving the output terminal 550 from alogical l to a logical O, a negative-going transition which is conveyedby conductor 56a to the clock pulse input 560 of the flipflop 56. Thenegative going clock pulse transfers the logical I previously storedwithin the masterslave flipflop 56 to the Q output terminal 56e.

Presence of a logical l at the terminal 56e permits the flip-flop 56 toopen, and alows the clock pulses from the oscillator 51 to appear at theterminal 57d as output pulses. The output pulses are furnished to thedriver/- buffer 32 over the conductor 57g and pass from thedriver/buffer 32 to the switch 16 to cause pulses of electrical courrentto be sent through the earth in the vicinity of the well, as has beenpreviously set forth. Each of the output pulses from the terminal 57dare supplied to the counter 52c by the conductor 57f and cause a downardbinary count of 1 in response to each pulse. Counter 52 countsdownwardly until the input count has been depleted, and at this timepresents a borrow signal, or logical O to the clear input 56h of theflip-flop 56 over the conductor 52f. Presence of a logical O at theclear input terminal 56h drives the Q output terminal 56e of theflip-flop 56 to a logical O regardless of the inputs present at theinput terminals 56b, 56c and 56d. The logical O at the output terminal56e is presented to the clear input terminal 57:: of the blockingflip-flop 57 by the conductor 56g, and drives the Q output terminal 57dto a logical O regardless of the presence of the out put of oscillator51 at the input terminals 57a, 57b and 570 thereby blocking any furtherpulses from the oscillator 51 from reaching the driver/buffer 32 inresponse to the counter 52 having counted the predetermined number ofoutput pulses.

An input capacitor 41 (FIG. 4) of the receiver/buffer 40 is electricallyconnected in a parallel circuit with the magnetic coil 21a and the coil21b of the sensing coil 21 between the conductors 21c and 21d. Theimpedance value of the input capacitor 41 is chosen in order to tune thesensing coil 21 to be sensitive to the preselected frequency of thetransmitting section T. A pair of operational amplifiers 42 and 43connected in a cas- 'cade arrangement by a coupling capacitor 44 amplifythe signals provided across the input capacitor 41 and furnish theamplified signals over an output conductor 45 to the frequency selectivedigital filter 60. A feedback resistor 42a is connected between anoutput terminal 42b and an input terminal 420 of the amplifier 42 tolimit the gain of such amplifier. A variable feedback potentiometer 43ais connected between an output 43b and an input 430 of the amplifier 43to control the gain. The resistance value of the potentiometer 43a isadjustable in order to selectively adjust the gain as may be desired. Apotentiometer 46 is electrically connected be tween the output conductor45 and ground at the output 43b of the amplifier 43. The potentiometer46 is an impedance matching potentiometer to match the input impedanceof the frequency selective digital filter 60. It should be noted thatthe receiver/buffer 40 amplifies the incoming signal and furnishes suchincoming signal without modification of the duration or length of suchsignal to the frequency selective digital filter, since adjusting theduration of the incoming signal would cause the incoming signal to berejected by the filter, as wll be more evident hereinbelow.

The frequency selective digital filter 60 (FIG. 6) receives the signalsfrom the receiver/buffer 40 and rejects and excludes signals of otherthan the preselectd frequency being transmittted by the transmittersection T. The digital filter 60 includes the digital filter oscillator61, a pair of D-type control flip-flops 62 and 63, an output D-typeflip-flop 64, a pair of binary counters 65 and 66, a coding outputcircuit 67 and an output NAND gate 68. The control flip-flops 62 and 63respond to positive axis crossings in the input signal on the conductor45 and establish an interval during which the clock pulses from theoscillator 61 are counted by the binary counter 65 and 66. The frequencyof the oscillator 61 is chosen to be a predetermined constant multipleof the preselected frequency being transmitted by the transmitter T sothat a predetermined number of output pulses of such oscillator 61 willoccur between positive zero crossings of the input signal. In theembodiment illustrated in the accompanying drawings, the filteroscillator 61 has an output frequency 200 times the preselectedfrequency sent from the transmitter T. The coding circuitry 67 and theoutput NAND gate 68 permit a control signal to pass to the outputflip-flop 64 in response to a second positive zero crossing of the inputsignal at the end of one cycle of the input signal if the number ofclock pulses from the oscillator 61 counted in the counters 65 and 66 is198, 199 or 200. In this manner, only output signals of the preselectedfrequency are permitted to pass through the frequency selective digitalfilter 60, excluding and rejecting spurious signals and permittingaccurate and reliable control of the subsurface well equipment E by theapparatus A.

The input conductor 45 provides the input signal to a clock pulse input62a of the flip-flop 62. A D input 62b of the flip-flop 62 is connectedto ground in order that the flip-flop 62 will provide a logical O at a Qoutput 62c in response to a positive axis crossing at the clock pulseinput 6221 and a logical 1 output at a6 output 62d. A clear input 62e ismaintained at a logical 1 input in response to a bias voltage furnishedto the input 62e over a conductor 62f and a current limiting resistor600 from a positive power supply 60b.

An electrical conductor 62g connects the output 62c of the flip-flop 62to a D input 63a of the flip-flop 63.

A clock input 63b of flip-flop 63 is electrically connected by aconductor 63c and an output conductor 61a to receive the clock pulsesfrom the filter oscillator 61. A Q output 63d of the flip-flop 63 isconnected by a conductor 63c to a preset input 62h of the flip-flop 62.Presence of a logical O at the preset input 62h of the flip-flop 62 setsthe output 62c of the flip-flop 62 to a logical I level regardless ofthe esence ofa clockpulse at the input terminal 62a. A Q output 63f ofthe flip-flop 63 is connected by an electrical conductor 63g to a clearinput 65a of the counter 65 and a clear input 66a of the counter 66.Presence ofa logical l at the output terminal 63f of the flip-flop 63clears the count from the counter 65 and 66. A clear input 63h of theflip-flop 63 is maintained at a logical l by the power supply terminal bthrough the current limiting resistor 60a to prevent the output 63f ofthe flip-flop 63 from being driven to a logical l at the improper times.A preset input 63i of the flip-flop 63 is connected by a conductor 63jto the output 62d of the flip-flop 62. Presence of a logical O at theoutput 62d when con ducted to the input 631 of the flip-flop 63 sets theoutput 63d of the flip-flop 63 to a logical I.

An electrical conductor 61b provides the clock pulses from theoscillator 61 to an up count input b of the binary counter 65 causingthe binary counter 65 to count the pulses from the oscillator 61. A downcount input 650 and a plurality of input terminals 65d of the counter 65are maintained inactive by the presence of a logical l at such inputsfrom the positive power supply terminal 60b, the current limitingresistor 60a and an electrical conductor 60c. In a like manner, a downcount input 666 and a plurality of input 66d of the counter 66 aremaintained in an inactive state by the presence of a logical l on theconductor 600.

The binary counter 65 counts the pulses from the oscillator 61 andprovides a binary indication of such counter on a plurality of outputterminals 65g. A carry output terminal 65f of the counter 65 provides asignal to an up count input 66b of the counter 66 when the counter 65has counted to its capacity, and allows the counter 66 to begin countingin conjunction with the counter 65 in order to increase the countingcapacity of the digital filter 60. A carry output 66fof the counter 66is connected to a load input 65:: and a load input 66e of the counter 65and 66, respectively, to lock the counter 65 and 66 at the maximumcounting capacity of such counters in the event that the maximumcounting capacity of such counters is reached in order to preventrecycling and erroneous output counts from the counter 65 and 66.

The coding circuit 67 includes an inverter 67a connected to the 4 outputof the counter 65, an inverter 67b connected to the 32 output of thecounter 66, an inverter 670 connected to the 16 output of the counter 66and a two input NAND gate 67d connected to the 2 and 1 outputs of thecounter 65. The coding circuits 67 are selected to provide apredetermined input signal to the output NAND gate when the counters 65and 66 have reached a predetermined count. In the embodiment illustratedin FIG. 6, the coding circuit 67 will furnish an electrical signal tothe NAND gate 68 driving the output 68a of the NAND gate 68 to a logical0 when the output count of the counter 65 and 66 is a decimal 200, 201or 202. Other coding circuits may be used in accordance with thefrequency of oscillator 61.

An electrical conductor 68b connects the output 62d of the flip-flop 62to an input of the NAND gate 68. The output terminal 62d of theflip-flop 62 is a logical I for the first clock pulse cycle of theoscillator 61 after the positive going transition in the input signal onthe conductor 45 is received at the clock input 68 of the flip-flop 62.Subsequent to such first clock cycle of the oscillator 61, the output63d of the flip-flop 63 is driven to a logical O, which is furnhised tothe preset input 62h of the flip-flop 62 returning the output 62c of theflip-flop 62 to a logical l and the output 62b of the flipflop 62 to alogical 0.

The logical 1 during the one cycle of the oscillator 61 previously setforth serves as a strobe or scan signal for the NAND gate over theconductor 68b. During the presence of such logical l on the conductor6811, the output count of the counter 65 and 66 as modified in thecoding circuitry 67 will drive the output 68a of the gate 68 to alogical only if the count of the counter 65 and 66 is 200, 201 or 202,as has been previously set forth.

At the end of the scan or strobe pulse on the conductor 6811, theoscillator 61 will energize a clock input 64a of the output flip-flop64, transferring the signal present at the output 68a of the gate 68 toa D input 64b of the flip-flop 64 over an electrical conductor 680. Ashas been set forth previously, the output 680 of the gate 68 is alogical 0 if the predetermined count corresponding to the duration of aninput signal of the predetermined frequency has occured between positiveaxis crossings of the input signal present on the conductor 45. Thepresence of a logical O on the input 64b of the flip-flop 64 causes a 0output 640 of the flip-flop 64 to assume a logical O in responsethereto. If the count of the. counter 65 and 66 as modified in thecoding circuitry 67 is not the preselected number 200, 201 or 202, theoutput of the NAND gate 68 on the input 64b of the flip-flop 64 is alogical l, and such logical l is transferred to the Q output 64c.

The Q output terminal 640 of the flip-flop 64 furnishes the output ofthe frequency selective digital filter 60 to the coded station controlcircuit 70 over an output conductor 69. The output signal of the digitalfilter 60. present on the conductor 69 is normally a logical I level,and is a logical 0 only if the duration of the input signal furnished tothe digital filter 60 by the receiver/- buffer 4.0 over the conductor 45is of a duration corresponding to the period of the preselectedfrequency of the transmiter T. Accordingly, the digital filter 60excludes and rejects unwanted and spurious signals and provides reliableand accurate control of the subsurface well equipment E.

The coded station control circuit 70 (FIG. 7) includes a timing controlcircuit 71, a binary counter 72, a coding gate circuit 73, a pair ofcontrol output generator flip-flops 74 and 75 and a power supply resetcircuit 76. The control circuit 70 receives pulses over the conductor 69from the filter 60, with the timing circuit 71 providing a timingcontrol pulse in response to the first incoming pulse. The timingcontrol pulse limits the time of receipt of pulses to a predeterminedtime interval in order that spurious and undesired signals are notcounted or received. The binary counter 72 counts the number of theincoming-pulses on the conductor 69 until cleared by the timing controlcircuit 71 at the end of the time interval transfers the output count ofthe counter 72 through the coding gates 73 to the control outputgenerators 74 and 75. The generators 74 and 75 provide an output pulseover conductors 77 and 78, respectively in response to the presence of apredetermined code at their inputs, and furnish the signal over theconductor 77 and 78 to the switch mounted with the equipment E to becontrolled by the apparatus of the present invention. The power supplyreset circuit 76 rests the control output generator 74 and 75 and thetiming circuit 71 when the subsurface equipment portion S of theapparatus A is initially energized at the surface of the earth beforebeing lowered into the well to operate the equipment E, as will be moreevident hereinbelow.

The timing circuit 71 is a retriggerable monostable multivibrator withclear integrated circut, such as for example a Texas Instruments PartNo. SN74l22. The timing circuit 71 is connected to the conductor 69 at apair of inputs 71a by a conductor 69a, A high to low transistion on theconductor 79, formed in response to the presence of a pulse of thepreselected frequency sensed by the digital filter 60 causes the timingcircuit 71 to form a positive going pulse at such time at a Q output 71bthereof. A 6output 71c provides an output signal which is the invertedsignal of the Q output 71b, and forms a negative going, logical 0 pulseat the'same time that the output 71b forms the positive going pulse. Theduration of the pulse formed in the timing circuit 71 is controlled byby an external resistor 71d and an external capacitor 712. The resistor71d and capacitor 71e receive current from a power supply terminal 71fand permit the timing circuit 71 to provide an output pulse until thecurrent from the power supply 71f through the presistor 71g charges thecapacitor 712 to a level to cause the control circuit 71 to terminatethe positive output signal from the output terminal 71b and provide apositive output signal from the output terminal 71c.

An electrical conductor 69b connects an up count input 72a of the binarycounter 72 and furnishes the pulses of the preselected frequency fromthe digital filter 60 to the binary counter 72. The binary counter 72counts the number of such pulses furnished to the control circuit by thefilter 60 and provides a binary output count at a plurality of outputterminals 72b to the coding circuit 73. A clear input terminal 72c ofthe counter 72 is connected to the output 710 of the timing circuit 71by a conductor 71g and responds to the transition to a logical O of theoutput terminal 710 in response to the initial incoming pulse to clearthe binary counter 72 and begin a new count in response to the incomingpulses.

A down count input 72d of the counter 72 and a plurality of inputterminals 72e of the counter 72 are pro vided with a logical I from apositive power supply terminal 76a through a current limiting resitor76b to prevent the counter 72 from downward counting and to load in themaximum output count of the binary count and prevent recycling of theconter should the maximum count be exceeded. A carry output 72f of thecounter 72 is connected to a load input 72g of the counter 72 andprovides an output signal in response to the counter 72 reaching itsmaximum count, which is furnished to the load input 72g. The inputsignal at the load input 72g causes the logical 1" present at the inputterminal 72e of the counter 72 to be loaded into the counter, andprevents further counting by the counter 72 when the maximum count ofsuch counter has been reached. The coding circuitry 73 receives theoutput from the output terminal 72b of the counter 72 and providescontrol signals to the control output generator 74 and 75 in response tothe presence of a predetermined code output from the counter 72. Thecoding control circuit 73 includes a plurality of inverters 73g, 73h,73i and 73 The AND gates 73b, 73 c, 73eand 73f are further electricallyconnected to the output 71b of the timing circuit 71 by an electricalconductor 71h. The conductor 71h provides the negative-going transistionof the signal present at the output terminal 71b at the termination ofthe time interval determined by the resistor 71d and 71e of the timingcircuit 71 to the above-reference AND gates and to a clock pulse input74a and a clock pulse input 75a of the control output generatorflip-LOPS 74 and 75, respectively The negative-going transition servesas a strobe or read-in signal and causes the output of the outputterminal 72b of the counter 72 to be transferred to the control outputgenerator flip-flops 74 and 75 in response to a preselected coded numberof pulses of the predetermined frequency being received by the filter 60and transferred to the control circuit 70.

A J input terminal 74b of the flip-flop 74 receives a logical 1 inputsignal from the AND gates 73b, 73a and the inverters 73g and 73h whenthe output count of the counter 72 is a binary count corresponding tothe decimal number 3 at the time of the strobe signal on the conductor71h. An K input 740 of the flip-flop 74 receives a logical I from theAND gates 73a and 73c and the inverters 73g and 7 3j at the time of thestrobe signal if the binary count and the counter 72 corresponds to adecimal 6. A 1 input 75b of the flip-flop 75 receives a logical I fromthe AND gates 73d and 73e and the inverters 73h and 73i at the time ofthe strobe signal on the conductor 71h if the binary count of thecounter 72 corresponds to a decimal 9. A K input 750 of the flipflop 75receives a logical I from the AND gates 73eand 73 f and the inverters731' and 73j at the time of the strobe signal on the conductor 71h ifthe output count of the counter 72 corresponds to a decimal 12.

The output control generators 74 and 75 thus individually respond to apreselected code signal corresponding to a preselected number of pulsesof the predetermined frequency sensed by the digital filter 60 andfurnished to the control circuit 70. The control output flip-flop 74provides a logical l at a Q output 74d at the time of the strobe signalover a conductor 77 to the switch in the equipment E in respone to atransmission and receipt of three pulses of the predetermined frequency.Transmission, receipt, filtering and counting of six pulses during thetime interval established by the timing circuit 71 will cause a logicalsignal to be present at the output 74d and furnished to the switch inthe equipment E, reversing the operation of such switch. In a likemanner, a Q output terminal 75d of the flip-flop 75 provides a logical Iover a conductor 78 to a switch controlling a second well control toolor equipment to be controlled by the apparatus A when nine pulses of thepredetermined frequency have been transmitted, received, filtered andcounted by the subsurface portion S of the apparatus A. When l2 pulsesare transmitted, received, filtered and counted during the time intervalcontrol by the timing circuit 71, the output terminal 75d provides alogical 0 signal over the output conductor 78 to the switch in thesecond piece of equipment, reversing the operation controlled by theswitch.

The power reset circuit 76 includes a current limiting resistor 760which provides electrical current from the positive power supplyterminal 76a to a pair of inputs 76d of an AND gate 76e. A resistor 76fand a capacitor 76g prevent the current from the resistor 760 fromreaching the inputs 76d of the gate 76e until the capacitor 76g hascharged to a sufficient level. The resistance value of the resistor 76fand the capacitance value of the capacitor 76g are chosen to be apreselected value to establish a time during which the inputs 76d of thegate 76e receive very little current, thus providing a logical 0 over anoutput conductor 76h to a clear input 761' of the timer circuit 71 and aclear input 74e of the flip-flop 74 and a clear input e of the flip-flop75. The duration of the time for the R-C combination of resistor 76f andcapacitor 76g provides a safety feature by disabling the timing circuit71 and the output generator 74 and 75 due to the presence ofa logical Oon the inputs 71e, 74e and 75e. The presence ofa logical O on theconductor 76h inhibits the input and receipt of signals by the timingcircuit 71 on the input conductor 69a. Simiarly, the presence of alogical O on the conductor 76h prevents the presence of a logical l atthe output 74d and 75d of the flip-flops 74 and 75. The presence of such0 does prevent inadvertent receipt of signals or actuation of thecontrol output generator 74 and 75 when the apparatus is at the surfacebefore being inserted into the well, thus providing a safety feature andpreventing accidents or damage to equipment or personnel in the area ofthe well. After the passage of time sufficient to allow the currentthrough the resistor 760 to charge the capacitor 76g, the conductor 76his driven to a logical I level in response to the current at the input76d of the gate 76e, permitting the timing circuit 71 and the outputgenerator 74 and 75 to oper ate in the manner previously set forth inresponse to input signals.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape, materials, wiring connections and contacts as well as in thedetails of the illustrated circuitry and construction may be madewithout departing from the spirit of the invention.

We claim:

1. An appartus for controlling the operation of subsurface well drillingand well control equipment, comprising:

a. transmitter means for sending a predetermined number of electricalcurrent pulses of a preselected frequency through the earth in thevicinity of the subsurface well equipment; and

b. subsurface equipment control means, comprising: 1. coil means mountedwith the subsurface well equipment for sensing the transmitted pulses;

2. selective filter means for excluding and rejecting signals other thanthe preselected excluding frequency sensed by said coil means;

3. control circuit means responsive to the predetermined number ofpulses for generating a control signal, said control circuit meansincluding timing means for deactivating said control circuit means inresponse to passage of a predetermined time interval wherein stray andspurious signals occuring outside the time interval are prevented fromgenerating a control signal; and

4. switch means repsonsive to the control signal for controllingoperation of the subsurface well equipment.

2. The structure of claim 1, wherein said transmitter means includes:

transmitter counter means for receiving selected input counts, saidcounter means controlling said transmitter means and permittingtransmission of selected predetermined numbers by said transmitter meansin accordance with the input count.

3. The apparatus of claim 1, wherein said selective filter meanscomprises:

digital filter means for timing the period of the signals sensed by saidcoil means, said digital filter means blocking signals by durationoutside the frequency limit of said filter means, wherein stray andspurious signals are prevented from reaching said control circuit meansand causing an erroneous signal to be generated.

4. The structure of claim 1, wherein said control circuit meanscomprises:

a plurality of control output means, each of said output meansresponding to an individual preselected code wherein plural selectedsubsurface equipment operations are individually controlled in responseto the presence of the individual preselected codes.

5. The structure of claim 1, wherein said control circuit meanscomprises:

a. receiver counter means for counting the pulses sensed by said coilmeans; and

b. means for providing an output signal in respone to a predeterminedcount in said receiver counter means to control the subsurface wellequipment.

6. A method of controlling the operation of subsurface well drilling andwell equipment, comprising the steps of:

a. sending a predetermined number of pulses of electrical current of apreselected frequency through the earth in the vicinity of thesubsurface well equipment;

b. sensing the transmitted pulses;

c. excluding signals other than the preselected frequency of transmittedpulses;

d. generating a control signal in response to the presence of thepredetermined number of pulses;

e. limiting the time interval of said step of generating to preventstray and spurious signals from being included in said step ofgenerating; and

f. controlling operation of the subsurface well equipment in response tothe control signal.

7. The method of claim 6, further including the steps a. receiving aselected input count; and

b. transmitting pulses of electrical current of the preselectedfrequency equal in number to the selected input count during said stepof sending.

8. The method of claim 6 whrein said step of excluding includes thesteps of:

a. timing the period of the signals received during said step ofsensing; and

b. blocking signals of time duration outside the limits of thepredetermined frequency of the pulses formed during said step ofsensing.

9. The method of claim 6, wherein said step of controlling comprises thestep of:

controlling a selected one of pulural subsurface equipment operations inaccordance with the number of pulses sent during said step of sending.

10. The method of claim 6, wherein said step of generating compriss thesteps of:

a. counting the sensed pulses; and

b. generating a control signal in response to a predetermined count fromsaid step of counting.

11. An apparatus for controlling the operation of subsurface welldrilling and well control equipment, comprising:

a. transmitter means for sending a predetermined number of electricalcurrent pulses of a preselected frequency through the earth in thevicinity of the subsurface well equipment; and

b. subsurface equipment control means, comprising: 1. coil means mountedwith the subsurface well equipment for sensing the transmitted pulses;

2. selective filter means for excluding and rejecting signals other thanthe preselected frequency sensed by said coil means, said selectivefilter means comprising digital filter means for timing the period ofthe signals sensed by said coil means, said digital filter meansblocking signals of duration outside the frequency limit of said filtermeans, wherein stray and spurious signals are prevented from reachingsaid control circuit means and causing an erroneous signal to begenerated;

3 control circuit means responsive to the predetermined number of pulsesfor generating a control signal, said control circuit means includingtiming means for deactivating said control circuit means in response topassage of a predetermined time interval wherein stray and spurioussignals occuring outside the time interval are prevented from generatinga control signal; and

4. switch means responsive to the control signal for controllingoperation of the subsurface well equipment.

1. An appartus for controlling the operation of subsurface well drillingand well control equipment, comprising: a. transmitter means for sendinga predetermined number of electrical current pulses of a preselectedfrequency through the earth in the vicinity of the subsurface wellequipment; and b. subsurface equipment control means, comprising: 1.coil means mounted with the subsurface well equipment for sensing thetransmitted pulses;
 2. selective filter means for excluding andrejecting signals other than the preselected excluding frequency sensedby said coil means;
 3. control circuit means responsive to thepredetermined number of pulses for generating a control signal, saidcontrol circuit means including timing means for deactivating saidcontrol circuit means in response to passage of a predetermined timeinterval wherein stray and spurious signals occuring outside the timeinterval are prevented from generating a control signal; and
 4. switchmeans repsonsive to the control signal for controlling operation of thesubsurface well equipment.
 2. selective filter means for excluding andrejecting signals other than the preselected excluding frequency sensedby said coil means;
 2. The structure of claim 1, wherein saidtransmitter means includes: transmitter counter means for receivingselected input counts, said counter means controlling said transmittermeans and permitting transmission of selected predetermined numbers bysaid transmitter means in accordance with the input count.
 2. selectivefilter means for excluding and rejecting signals other than thepreselected frequency sensed by said coil means, said selective filtermeans comprising digital filter means for timing the period of thesignals sensed by said coil means, said digital filter means blockingsignals of duration outside the frequency limit of said filter means,wherein stray and spurious signals are prevented from reaching saidcontrol circuit means and causing an erroneous signal to be generated; 3control circuit means responsive to the predetermined number of pulsesfor generating a control signal, said control circuit means includingtiming means for deactivating said control circuit means in response topassage of a predetermined time interval wherein stray and spurioussignals occuring outside the time interval are prevented from generatinga control signal; and
 3. The apparatus of claim 1, wherein saidselective filter means comprises: digital filter means for timing theperiod of the signals sensed by said coil means, said digital filtermeans blocking signals by duration outside the frequency limit of saidfilter means, wherein stray and spurious signals are prevented fromreaching said control circuit means and causing an erroneous signal tobe generated.
 3. control circuit means responsive to the predeterminednumber of pulses for generating a control signal, said control circuitmeans including timing means for deactivating said control circuit meansin response to passage of a predetermined time interval wherein strayand spurious signals occuring outside the time interval are preventedfrom generating a control signal; and
 4. switch means repsonsive to thecontrol signal for controlling operation of the subsurface wellequipment.
 4. The structure of claim 1, wherein said control circuitmeans comprises: a plurality of control output means, each of saidoutput means responding to an individual preselected code wherein pluralselected subsurface equipment operations are individually controlled inresponse to the presence of the individual preselected codes.
 4. switchmeans responsive to the control signal for controlling operation of thesubsurface well equipment.
 5. The structure of claim 1, wherein saidcontrol circuit means comprises: a. receiver counter means for countingthe pulses sensed by said coil means; and b. means for providing anoutput signal in respone to a predetermined count in said receivercounter means to control the subsurface well equipment.
 6. A method ofcontrolling the operation of subsurface well drilling and wellequipment, comprising the steps of: a. sending a predetermined number ofpulses of electrical current of a preselected frequency through theearth in the vicinity of the subsurface well equipment; b. sensing thetransmitted pulses; c. excluding signals other than the preselectedfrequency of transmitted pulses; d. generating a control signal inresponse to the presence of the predetermined number of pulses; e.limiting the time interval of said step of generating to prevent strayand spurious signals from being included in said step of generating; andf. controlling operation of the subsurface well equipment in response tothe control signal.
 7. The method of claim 6, further including thesteps of: a. receiving a selected input count; and b. transmittingpulses of electrical current of the preselected frequency equal innumber to the selected input count during said step of sending.
 8. Themethod of claim 6 whrein said step of excluding includes the steps of:a. timing the period of the signals received during said step ofsensing; and b. blocking signals of time duration outside the limits ofthe predetermined frequency of the pulses formed during said step ofsensing.
 9. The method of claim 6, wherein said step of controllingcomprises the step of: controlling a selected one of pulural subsurfaceequipment operations in accordance with the number of pulses sent duringsaid step of sending.
 10. The method of claim 6, wherein said step ofgenerating compriss the steps of: a. counting the sensed pulses; and b.generating a control signal in response to a predetermined count fromsaid step of counting.
 11. An apparatus for controlling the operation ofsubsurface well drilling and well control equipment, comprising: a.transmitter means for sending a predetermined number of electricalcurrent pulses of a preselected frequency through the earth in thevicinity of the subsurface well equipment; and b. subsurface equipmentcontrol means, comprising: